Quantifying Submarine Groundwater Discharge From St. Catherines Island, Georgia

Document Type


Publication Date

Fall 2014


St. Catherine’s Island is a relatively pristine barrier island located ~80 km south of Savannah, GA. Its coastline is dominated by tidal marsh and wetlands, with some sandy beaches. The island has a locally recharged surficial aquifer that is stratigraphically above the confined Upper Floridan aquifer. The surficial aquifer naturally discharges groundwater to the nearby estuary as submarine groundwater discharge (SGD). SGD has been shown to be an important source of fresh to brackish water and dissolved inorganic nutrients to estuaries worldwide. To better understand the chemistry of this discharging water, we periodically collected water samples from six surficial wells and four Upper Floridan wells located on St. Catherine’s Island. We also collected nine samples from active groundwater seeps on the island’s sandy beaches. All samples were analyzed for radon-222, a tracer of SGD. The well samples were also analyzed for common ions. Our results suggest that the active groundwater seeps are fed by the surficial aquifer. A preliminary radon-222 survey of the estuary surrounding the northern half of the island indicates that groundwater also diffusely discharges from the surficial aquifer. Our future research plans are to characterize the major ion and dissolved inorganic nutrient chemistry of the groundwater seeps issuing from the beaches. We will also conduct seasonal radon-222 surveys of estuary waters around the entire island to better characterize the locations and fluxes of groundwater discharge and dissolved inorganic nutrients to the nearby estuary.


Southeastern Estuarine Research Society Fall Meeting (SEERS)


Carolina Beach, NC